Xiaoyuan Chen

Bio: Xiaoyuan Chen is an academic researcher from National University of Singapore. The author has contributed to research in topics: Physics & Photothermal therapy. The author has an hindex of 149, co-authored 994 publications receiving 89870 citations. Previous affiliations of Xiaoyuan Chen include Brown University & University of Southern California.

LC/MS evaluation of metabolism and membrane transport of bombesin peptides

Abstract: Two bombsin peptides, GRPR agonist [Aca-QWAVGHLM-NH2] and antagonist [fQWAVGHL-NHEthyl] were evaluated. We employed the highly sensitive Waters Q-Tof Premier MS coupled with a UPLC system to identify the metabolites produced by rat hepatocytes or PC-3 human prostate cancer cells; and we utilized the AB/MDS 4000 Q-Trap LC/MS/MS system with highly sensitive quantitative and qualitative performance, to quantitatively analyze the internalization of GRPR agonist and antagonist in PC-3 cells. The major metabolites of both GRPR agonist and antagonist were the result of peptide bond hydrolysis between W and A which was demonstrated by observation of the N-terminal fragment m/z 446 (Aca-QW-OH) for agonist and m/z 480 (fQW-OH) for antagonist. Both peptides were also hydrolyzed between A and V which formed peaks m/z 517 [Aca-QWA-OH] and m/z 555 (VGHLM-NH2) for the agonist and m/z 551 [fQWA-OH] and m/z 452 (VGHL-NHEthyl) for the antagonist. The peptide agonist also formed a unique metabolite that resulted from hydrolysis of the C-terminal amide. The antagonist showed significantly slower metabolism as compared to the agonist in both rat hepatocytes and PC-3 cells. The antagonist also showed significantly lower PC-3 cell internalization rate than that of the agonist. In conclusion, the metabolism profiles of both GRPR agonist and antagonist peptides were identified by LC/MS. The antagonist peptide was more stable than the agonist peptide in rat hepatocyte incubation. One major factor could be the hydrolysis-resistant C-terminal L-NHEthyl group compared with the unsubstituted amide of the agonist. Another factor could be different amino acid sequences of the agonist and antagonist that may also influence the enzymatic hydrolysis. The antagonist ligand is potentially more useful for receptor-targeted imaging due primarily to its higher metabolic stability.

Precision measurements of decay parameters and CP asymmetry in Λ decays

Abstract: Based on 10 billion J/ψ events collected in the BESIII experiment, the phase angle ∆Φ associated with hyperon polarization in Λ / ¯Λ production, and the decay parameters α − for Λ → pπ − and α + for ¯Λ → ¯ pπ + are studied in the process J/ψ → (Λ → pπ − )(¯Λ → ¯ pπ + ). The free parameters of the joint angular distribution are determined by means of a maximum likelihood fit, and the results are: ∆Φ = 0 . 7521 ± 0 . 0042 ± 0 . 0080, α − = 0 . 7519 ± 0 . 0036 ± 0 . 0019, and α + = − 0 . 7559 ± 0 . 0036 ± 0 . 0029. The average value of the Λ decay parameter is α avg = 0 . 7542 ± 0 . 0010 ± 0 . 0020. The CP asymmetry observable A CP

Redox-responsive dual chemophotothermal therapeutic nanomedicine for imaging-guided combinational therapy

Abstract: Chemotherapy is currently the major therapeutic method against cancer. However, chemo drugs are usually lacking in specificity towards cancer cells over normal cells. In this study, we prepared a novel multifunctional trimeric prodrug by linking the chemo drug camptothecin (CPT) and the exceptionally photostable near infrared (NIR) croconaine dye (CR) via a glutathione (GSH)-sensitive disulfide linker. Compared with CPT, our novel trimeric CR-(SS-CPT)₂ is more hydrophobic and bulky, making it highly efficient to be encapsulated into biocompatible polymeric nanocarriers. The prodrug underwent rapid drug release specifically in cancer cells with high GSH concentration. The hyperthermia produced by CR upon laser irradiation could further accelerate the break of disulfide bonds, which makes the release of CPT even more controllable. We further loaded CR-(SS-CPT)₂ into folate modified lipid–polymer nanoparticles, which demonstrated high in vivo tumor accumulation and retention. The biodistribution of these nanoparticles can be directly monitored in real time via NIR fluorescence and photoacoustic imaging. Under imaging guided chemo- and photothermal-synergistic therapy, the tumors were completely ablated with no recurrence. The design not only highly enhanced the therapeutic specificity and efficiency of CPT, but also provided an “all in one” nanomedicine for imaging-guided dual modality therapy.

I and i

Abstract: There is, I think, something ethereal about i —the square root of minus one. I remember first hearing about it at school. It seemed an odd beast at that time—an intruder hovering on the edge of reality. Usually familiarity dulls this sense of the bizarre, but in the case of i it was the reverse: over the years the sense of its surreal nature intensified. It seemed that it was impossible to write mathematics that described the real world in …

疟原虫var基因转换速率变化导致抗原变异[英]／Paul H, Robert P, Christodoulou Z, et al//Proc Natl Acad Sci U S A

Abstract: 抗原变异可使得多种致病微生物易于逃避宿主免疫应答。表达在感染红细胞表面的恶性疟原虫红细胞表面蛋白1（PfPMP1）与感染红细胞、内皮细胞、树突状细胞以及胎盘的单个或多个受体作用，在黏附及免疫逃避中起关键的作用。每个单倍体基因组var基因家族编码约60种成员，通过启动转录不同的var基因变异体为抗原变异提供了分子基础。

Chemistry and properties of nanocrystals of different shapes.

Abstract: The interest in nanoscale materials stems from the fact that new properties are acquired at this length scale and, equally important, that these properties * To whom correspondence should be addressed. Phone, 404-8940292; fax, 404-894-0294; e-mail, mostafa.el-sayed@ chemistry.gatech.edu. † Case Western Reserve UniversitysMillis 2258. ‡ Phone, 216-368-5918; fax, 216-368-3006; e-mail, burda@case.edu. § Georgia Institute of Technology. 1025 Chem. Rev. 2005, 105, 1025−1102